I am not familiar with your crossover layout, but is it possible that the inductor is causing crosstalk with other components? Are there other inductors or coils near it? Is it directly next to the high-frequency section of the crossover?
You may want to try moving the location and orientation of the inductor - if it is lying flat, try standing it on its side and turning it to point in different directions, and see if the noise decreases.
You may want to try moving the location and orientation of the inductor - if it is lying flat, try standing it on its side and turning it to point in different directions, and see if the noise decreases.